The synthesis of aromatic diazatricycles from phenylenediamine-bis(methylene Meldrumʹs acid) derivatives

The thermocyclisation of phenylenediamine-bis(methylene Meldrumʹs acid) derivatives has been investigated. Those of o-phenylenediamines give 1,10-phenanthroline derivatives, while those of m- and p-phenylenediamines lead to the preferential formation of angular diazatricycles. Thus, for example, the di-Meldrumʹs acid derivative of 2,5-dichloro-1,4-phenylenediamine gives, via ipso-substitution, the unexpected angular product .